Range-finder.



N0. 69!,247 Patented Ian. 14, I902.

C. DAVIS.

RANGE FINDER. (Application fil ed Oct. 30. 1901) 2 Sheets-Sheet I.

(No Model.)

uuzufoz no: Nonms PETERS ca. wmouma. WASHINGTON. 04 t.

UNITED STATES PATENT ()FFICE.

OLELAND DAVIS, OF THE UNITED STATES NAVY,

RANGE-FINDER.

SPECIFICATION forming part of Letters Patent N 0. 691,247, dated January 14, 1902.

Application filed October 30, 1901. Serial No. 80,550. (No model.)

To ally/horn. it may concern:

Be it-known that I, CLELAND DAVIS, a lientenant in the United States Navy, stationed at Washington, in the District of Columbia,

have invented certain new and useful Im-' gun-platform or of the enemy, or both, render frequent observations necessary; but it is also applicable for use with water-batteries or against troops in the field or for like purposes.

My invention will be understood by reference to the accompanying drawings, in which the same parts are indicated by the same letters throughout the several views.

Figure l is a diagram showing the theory of the instrument. Fig. 2 is a plan view showing one form of the instrument. Fig. 3 is a rear elevation showing the instrument mounted upon a movable base. Fig. 4: shows one means of elevating and depressing the telescope. Fig. 5 shows one form of adj ustable-plate indicating-ranges. Fig. 6 shows the invention applied to the sighting-hoods of a revolving turret. Fig. 7 shows the invention used on the broadside of a ship. Fig. 8 shows the invention used on either bow of the ship, and Figs. 9 and 10 are details showing one form of adjustable scale and means for adjusting the same.

I provide two telescopes, one of which is preferably of a large field and comparatively low magnifying power and the other of a small field and high magnifyingpower. These two telescopes are mounted on a rigid support and have their axes converging toward the target or object whose distance is to be determined. The angle between the vertical planes through the collimation-axes'of the two telescopes may be varied within limits and the scale indicating-ranges in the high-- powered telescope may be adjusted, as will be hereinafter described.

Referring now to Figs. 1 to 5, 0 represents the telescope having the larger field, which is provided with ordinary cross-hairs 0, (shown in dotted lines in Fig. 3,) which telescope is mounted on a support rigidly secured to the bar D. The telescope O, of small field or high magnifying power, is mounted on the opposite end of the bar D, and its support may be given a slight lateral trend by means of the worm-wheel K and worm 7c, operated by the thumb-screw K, or the support for this telescope may be secured fast to the bar D and the necessary adjustment given by means of the thumb-screw 0 moving the range-indicating plate C The bar D is mounted on the support E with the ball-andment will be understood by reference to Fig.

1, where M indicates the distance between the foci of the two telescopes O and 0, both of whichinclude in their respective fields the object P, the telescope 0 having its vertical cross-hair bisecting said object. The distance of the telescope G from this object P would then be R, and the distance may be expressed by the equationR=M cotangent 6. If the collimation-axis of the telescope O is in the vertical plane 0 Y at a known angle is from the position parallel to the vertical plane PC, then the object P' would subtend an angle go with the collimation-axis of the telescope O, and or would be equal to l97 This would enable us to determine mathematically the distance of the target; but in practice this distance is read from the scale C". In other words, we have a triangle in which one side M is known, one angle, preferably ninety degrees, is constant, and the other angle 6? is indicated by the measurements on the scale. The scale may be adjusted as shown in Figs. 2 and 5, or as will be hereinafter described with reference to Figs. 9 and 10, or in any other convenient way. Since the graduation on the scale depends upon the constant length M, which is the same for all ranges, and the variable angle (9, which depends on the range, the same scale may be used, no matter what may be the convergence of the collimationaxes of the two telescopes. If these axes are parallel or in the positions GP and OY, then it will only be possible to use half the field of the plate 0, and therefore the infinity-line would fall at the center of the plate and the lines indicating short ranges would be excluded from the plate altogether; but by having the collimation-axes of the two telescopes converging the lines indicating ranges may be ruled across the entire face of the plate. Furthermore, in practice the scale is ruled with regard to the known base M of the instrument, and then the axis of the telescope O is set approximately at that angle at which the field will include the known or expected position of the target when the target is bisected by the vertical cross-hair c. The telescope O is now clamped in this position, or, if preferred, it may be permanently set at this angle.

Now the plate C is adjusted by first swinging the bar D so that the-telescope C has its vertical cross-hair c on some point P whose range is accurately known. WVe will say that the range of the point P is eight hundred yards. Then adjust the plate C until the vertical line 8 is on this point P, and the instrument will be in adjustment and will stay in adjustment until put out by accident or rough usage. After the instrument is adj usted the distance of any other object within the limits of the instrument will be indicated on the proper range-indicating lines of the plate (3 when the vertical cross-hairs of the telescope O biseot that object.

WVhere the telescope O has a very high magnifying power with correspondingly small field, it may be desirable to so adjust the instrument that a portion only of the scale C shall be in or near the focus of the instrument, or, in other words, so that the reading got the instrument will be confined to comparatively short variations in the range.

Thus for a water-battery commanding a narrow passage it will only be desirable to use moving the plate O back and forth may be adopted, if desired. In this form of device that portion of the plate corresponding to the range may be kept at or near the focus of the instrument, and thus a very high power instrument with fine graduations may be used. It will of course be necessary to readjust the instrument on some object at a known distance whenever either the angle between the collimation-axes of the telescopes is varied or whenever the plate 0 is moved; but this may be rapidly and frequently done when desired.

The form of device shown in Figs. 2 and 3 is intended more especially for land use,while that in Figs. 6, '7, and 8 represents the invention as used on shipboard.

A represents a revolving turret of the ordinary form, and in the sighting-hoods B, B, and B are located the telescopes C and C, and, if desired, a third telescope 0 generally similar to C, already described. The telescope C is used to correspond with'the telescope 0, already described,and C and O are the rangeindicating instruments. I show two of these rangeindicating telescopes; but one alone may be used, and, moreover, it .it is desired to use a longer base the finding instrument 0 may be put in the sighting-hood B when we will have the distance between the centers of the sighting-hoods B and B as a base. In turning the turret to sight the guns the finding instrument 0 is brought on the target and the range-indicating instrument C or C will indicate the range without the necessity for any calculations.

In the form of instrument shown in Fig. 7 the sighting-telescope C and the range-indicator C are some distance apart, connected by call-bells H and H, operated by an electric battery H or some similar signaling de vice.

The ship is sheared 0E so that the target is brought in the field of the telescope O, and as soon as it is bisected by the cross-hairs of this telescope the observer there signals to the observer at the telescope 0', who immediately reads the range on the range-indicating plate.

The operation of the device shown in Fig. 8 is the same as that shown in Fig. 7, except that the two telescopes are on either bow of the vessel.

It will be obvious that the telescopes C and C may be located on shore at any known distance from each other and the instrument adjusted by sighting on an object at a known distance,fas already described. Then the ob server at C may signal to the observer at 0 when the mast of a ship is bisected by his cross-hair and the observer at C may read 01f the range. The scale C is always graduated IIO to correspond to the distance between the two telescopes, and this distance being constant and known the instrument may be adjusted, as before described, to use any particular part of the scale.

I do not mean to limit my invention to any particular mode of adjusting the convergence of the axes of the two telescopes or of adjusting the range-indicating plate in the second telescope, as many other variations in the mechanical arrangement of the parts may be used, if desired; but

What I claim, and desire to secure by Letters Patent of the United States, is

1. In a range-finder, the combination with a telescope provided with a vertical crosshair, of a second telescope located at a known horizontal distance from the first and having the vertical plane through its axis inclined toward the vertical plane through the axis of the first telescope, arigid connection between the mounts of the two telescopes, and a transparent plate with vertical lines to indicate ranges ruled thereon in the focus of the second telescope, on which plate the image of the object is thrown, substantially as described.

2. In a range-finder, the combination with a telescope provided with cross-hairs, of a second telescope located at a known horizontal distance from the first and having the vertical plane through its axis inclined toward the vertical plane through the axis of the first telescope, means for adjusting the angle between the axes of the two telescopes, a rigid connection between the mounts ot' the telescopes, and a transparent plate with vertical lines representing ranges ruled thereon in the focus of the second telescope on which plate the image of the object is thrown, substantially as described.

3. In a range-finder, the combination with a telescope provided with a vertical crosshair, of asecond telescope located at a known horizontaldistance from the first and having the vertical plane through its axis in adj ustable relation to the vertical plane through the axis of the first telescope, a rigid connection between the mou nts of the two telescopes, and a transparent plate with vertical lines indicating ranges ruled thereon in the focus of the second telescope, on which plate the image of the object is thrown, with means for moving said platelaterally, substantially as described.

4. In a range-finder, the combination with a telescope of large field provided with a vertical cross hair, of a second telescope of smaller field and high magnifying power located at a known horizontal distance from the first and having the vertical plane through its axis in adjustable relation to the vertical plane through the axis of the first telescope, a rigid connection between the two mounts of the two telescopes, and a transparent plate with vertical lines indicating ranges ruled thereon in the focus of the second telescope, on which plate the image of the object is thrown, with means for moving said plate laterally, substantially as described.

In testimony whereof I affix my signature in presence of two witnesses.

CLELAND DAVIS. Witnesses:

GRAFTON L. MCGILL, PERCY O. BOWEN. 

